Sergio Jerome Pettis (born August 18, 1993) is an American mixed martial artist who is currently signed in the Professional Fighters League. Previously, he fought in Bellator, where he competed in the Bantamweight division and became the Bellator Bantamweight Champion. Earlier in his career, Pettis also competed in the Ultimate Fighting Championship (UFC), fighting in both Bantamweight and Flyweight divisions.

Pettis was born to Annette (née Garcia) and Eugene Pettis Jr. in Milwaukee, Wisconsin. Along with his older brother former UFC Lightweight Champion Anthony Pettis, who competes in the lightweight division, and oldest brother Reynaldo Pettis, he grew up in the south side of Milwaukee, Wisconsin.

Pettis' mother is of Mexican descent and his father is of Puerto Rican descent. To escape prejudice, his grandpa Eugenio Pérez anglicised the family name from Pérez to Pettis. Pettis was a student at Pius XI High School.

Pettis' father was fatally stabbed by a robber on November 12, 2003, at a friend's residence.

Pettis turned pro on September 10, 2011, against Kyle Vivian at Canadian Fighting Championship 7. He won via TKO in the first round.

On January 7, 2012, Sergio took on Mike Lindquist at Madtown Throwdown 26. He won via submission in round one.

Pettis fought Tom McKenna at LFC 53. He won via first round submission.

Pettis then took on Tony Zelinski at NAFC: Unleashed. He won via second-round TKO.